The addition of perfluoroalkane iodides CF.sub.3 (CF.sub.2).sub.n I, which are designated hereinafter by the generic term R.sub.F I, onto ethylenic or acetylenic compounds leads to products which are used as intermediates in synthesis; such as polyfluorinated halohydrins and epoxides.
Several processes are known, but these give only mediocre yields in the case of ethylenic or acetylenic alcohols and particularly in the case of allyl alcohol.
This addition can, for instance, be carried out by the use of radicals initiating the reaction by an elevation of temperatures (R. N. Haszeldine, J. Chem. Soc. 1953, p. 1199; U.S. Pat. Nos. 3,016,406 and 3,016,407), by irradiation with ultraviolet rays (R. N. Haszeldine's article cited above; J. D. Park, J. Org. Chem. 26, 1961, p. 2086, and D. Cantacuzene, J. Chem. Soc. Perkin I, 1977, p. 1365), or by means of azoic derivatives (N. O. Brace, J. Org. Chem. 27, 1962, p. 3027, and U.S. Pat. Nos. 3,083,224, 3,145,222, and 3,257,407).
It is likewise possible to catalyze the addition by Assher's system (J. Chem Soc. 1961, p. 2261), with the catalyst being a mixture of cuprous and cupric salts and of amines. This process was extended to fluorinated molecules by D. J. Burton (Tetrahedron Letters 1966, p. 5163), N. O. Brace (J. Org. Chem 44, 1979, p. 212) and described in French Pat. No. 2,103,459.
Although all of these systems make it possible to add R.sub.F I onto an ethylenic compound, they present the drawback of resulting only in mediocre and very variable yields, depending on the nature of the initiator and the nature of the olefin used. A universal catalyst does not exist and, in particular, there is no system capable of causing the quantitative addition of R.sub.F I onto ethylenic alcohols. Thus, the photochemical addition according to J. D. Park, or the process described in French Pat. No. 2,103,459, yield a degree of conversion of only 50-55% with allyl alcohol.